Take-off unit

Abstract

A withdrawal device for blow-molded film has an air turning bar with an air cushioned surface for transporting the film, and the bar surface includes at least in part a sintered material. The sintered material portion of the bar surface provides a region of increased friction for compressed air flow, thus more effectively guiding the withdrawn film in a flat and even form.

Description

[0001]This is a nationalization of PCT / EP03 / 014560 filed Dec. 19, 2003 and published in German.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention relates to a withdrawal device for films manufactured in a blow-molding process.[0004]2. Description of the Prior Art[0005]A withdrawal device for films manufactured in the blow-molding process is known, for instance from the patent specification DE 195 22 318 A1. After the film, for instance, a plastic tubular film emerging from an extruder has been laid flat, it is guided by means of air turning bars and deflecting rollers that as a rule reverse against one another and usually rotate around a common axis. After running through the withdrawal device the film is fed to a winding device on which it is wound into a roll for the purpose of collecting it and transporting it away easily.[0006]The air turning bars used in withdrawal devices of such type were frequently executed in a way allowing compressed air ...

AI Technical Summary

Benefits of technology

The present invention relates to an air turning bar for improving the stability of an air cushion used for transporting blow-molded films. The air turning bar has a surface with increased friction for compressed air flow, which helps guide the film smoothly and evenly. The rough texture of the sintered material on the bar surface causes this effect, reducing air leakage and lowering the energy requirement for the air cushion. The air turning bar can be manufactured with only the surface regions guiding the film comprising sintered material, reducing manufacturing expenses. The use of sintered ceramics is particularly advantageous. The air turning bar can also be molded in a concave form with a variable radius over an axial expansion. Overall, the invention provides a more effective and efficient air cushion for film transport.

Problems solved by technology

One problem in the known air turning bars is the uneven thickness of the air cushion over the axial width of the bar and / or the uneven force acting on the film due to the compressed air.

Consequently, in its center region the film exhibits a certain sag and can no longer be guided in a flat form.

The film in this center region is prone to the formation of wrinkles.

However, it turns out that the films that are guided in this manner cannot be wound up into a perfect roll.

In practice it has been proven even in case of this embodiment of the air turning bar that the air cushion between the turning bar and the film does not apply a sufficiently even force on the film.

Consequently the film cannot be guided with an even web tension across its width.